The present invention is directed to the use of an Ad Hoc peer-to-peer radio access system together with Time Division Duplex (TDD) as a way of maximizing the bits/hz/km2 for cellular systems. The invention is directed to radio access schemes and network architecture that allows radio access to be integrated with the fixed components of a conventional cellular system, PSTN, and the Internet. The objective is to make the system of the invention transparent to the features and services provided by the extraneous network infrastructure. The advantages of such a system to a cellular operator are that significantly less infrastructure is required, and that the RF spectrum is more efficiently utilized resulting in much lower building and operating costs.
Cellular communications systems have been deployed for over 20 years using a proven FDMA scheme that is very efficient for voice communications. Such schemes are employed by all current cellular systems including AMPS, TACS, NMT, GSM, IS-136 and IS-95. This same scheme is proposed for the next generation cellular systems named 3G.
With the arrival of laptop computers, portable digital assistants (PDAs) and high-tech cellular phones, consumers are beginning to request mobile data services in addition to traditional voice services. Some mobile data services have already been overlaid on top of FDMA cellular systems, but because of the inefficiencies of FDMA outlined below, these data services provide very limited bandwidth to the end user, which are typically 9600 baud in the current generation of cellular systems. Time Division Duplex (TDD) systems are typically used for packet data systems as they make much more efficient use of the available bandwidth in order to deliver a much higher effective data rate to the end user. TDD is typically used in fixed wired solutions or point-to-point wireless systems because it has its own spectrum limitations as described below. TDD systems, however, have not been deployed for voice systems.
FDMA provides a simple mechanism for guaranteeing quality of service and low latency for voice communication, but does so by inefficiently using the available spectrum. For example, a voice conversation between a mobile phone and a base station requires an up-link to send on and a down-link to receive on. Most conversations consist of one person talking while the other listens, with silent pauses in between. This results in channel utilization of less than 40%. In addition, FDMA employs a method that breaks the available spectrum into discrete blocks called channels. This provides a mechanism for reuse of spectrum using cells. Although there are different reuse schemes in use, they all fundamentally do the same thing. The geographic region for which coverage is required is broken down into a large number of cells. The set of available channels is broken up into at least 3, but typically 7, subsets, and divided up amongst the cells, so that there are no common frequencies in any adjacent cells, as seen in FIG. 1. The result of this reuse method is that the bits/hertz/km2 are, at best, only ⅓ the potential that is available for the spectrum allocated to the cellular operator. Spectral efficiency is a key economic factor in wireless communications because of the limited availability and high cost of spectrum. Wireless operators are constantly striving to improve spectral efficiency on these grounds, but cellular methodologies can only do this by deploying more, equally expensive, infrastructure.
The basic architecture of a cellular system is the same for all existing and proposed RF technologies. The international GSM architecture, as shown in FIG. 2, is used as a reference model. For North American systems IS-634 replaces GSM-A and IS-41 replaces GSM-MAP. The important factor is that modern cellular systems are decomposed into logical functional units, with well-defined interfaces between them.
The present invention removes the FDMA-based radio subsystems and radio interfaces, and replaces them with an Ad Hoc radio access system. The key component of the invention is how the system of the present invention is interlaced with the cellular system's infrastructure to provide a function of transparency to the cellular network operator and the mobile customer when the system of the invention is employed.
With respect to the using the system of the present invention as a stand-alone mobile radio network system, it is noted that although many forms of ad-hoc networking are extant, none allows for a peer-to-peer ad-hoc network to interwork with other networks, as that of the system of the present invention. The most widely known specification is that defined in the IEEE 802.11 standard. The system of the present invention may be applied to any 802.11 system, and would provide similar benefits. The system of the invention could also be applied to many other radio access schemes, such as Orthogonal Frequency Division Multiplexing (OFDM) in a similar manner. The present invention enhances the basic routing protocols and provides additional components required to allow for seamless integration with other telecommunications systems. As such, system would provide commercial mobile voice and mobile internet service to a user of the system.
In commonly-owned, copending patent application Ser. No. 09/815,157, filed on Mar. 22, 2001, entitled “Time Division Protocol for an Ad-Hoc, Peer-to-Peer Radio Network Having Coordinating Channel Access to Shared Parallel data Channels with Separate Reservation Channel”, there is disclosed a novel protocol for an ad-hoc, peer-to-peer radio network system having coordinating channel access to shared parallel data channels via a separate reservation channel. This network system having coordinating channel access to shared parallel data channels via a separate reservation channel is directed to a network system, such as the ad-hoc radio network system of the present application, where each node, or radio terminal, of the network is capable of serving as a node or hop of a routing path of a call from another, or to another radio terminal. In this system, communication between nodes or radio terminals is achieved using Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol with the addition of multiple parallel data channels serviced by one reservation channel. By dedicating a separate reservation channel for the multiple parallel data channels, collision-free access by all of the competing nodes or terminals of the service group of the network is greatly reduced. Communications between terminals or nodes is set up by information exchanged on the separate reservation channel, which information includes all of the call set-up information such as data channel desired to be used for transferring voice, video or data, the desired power level of at least initial transmission, messaging such as Request-to-Send (RTS), Clear-to-Send (CTS), Not-Clear-to-Send (NCLS), Acknowledgment (ACK) for indicating reception of the transmitted call, Non-Acknowledgment (NACK) for indicating improper reception of the call, etc. In this system, in order to further ensure fast, adequate and collision-free transmission and reception, besides a primary modem typically provided with the transceiver of each node or terminal, a secondary modem is also provided which is dedicated to the reservation channel. This system also provides for collision free transmission and reception between nodes or terminals by transmitting the reservation and data channels in time slots of time frames, with the information as to which time slot is to be used being included in the messaging transmitted by the reservation channel. Such a format not only provides collision-free transmission, but also allows for Quality-of-Service (QoS) for different types of Class-of-Service (CoS), Thus, not only may voice and video be transmitted, besides data, but voice and video transmission may be prioritized, so that when competing calls vie for a data channel, the delay-dependent voice or video transmissions will take precedence. This prioritization is accomplished by assigning prioritized calls for transmission in earlier time slots of a time frame. This network system ensures that every node or terminal of a service set of terminals has the most information regarding all of other terminals of that service set, so that the choice of data channel to be used, any required delay is transmitting the call, information on power level, and the like, are checked and updated by each terminal by a practically continuous monitoring of the reservation channel. The system of the invention utilizes protocol that provides collision-free channel access, which also emphasizes improving geographic reuse of the frequency spectrum. The ad-hoc, peer-to-peer radio system of this patent does not have, nor require, a base station, as conventional cellular systems, personal communications system (PCC), and the like, require; instead, each radio terminal forming part of the ad-hoc, peer-to-peer radio system may alternatively serve as a base station, in addition to being an ordinary link terminal of the radio system, whereby, if one such terminal serving as a base station should for some reason become inoperative, another terminal may take over and serve as the base station. In U.S. Pat. No. 5,943,322—Mayer, et al., which patent is incorporated by reference herein, the radio system thereof is for use in battlefield conditions, where personal voice communications is based on a time division duplex (TDD) technique in a code division multiple access (CDMA) system, is operated without a fixed base station, and is provided with simultaneous transmission of a communications channel and a control channel, each spread by different PN codes. The PN code facilitates restricting communications on the network to a particular voice-conversation mode and between identified radios. Transmissions are performed in a time division duplex manner in 62.5 milliseconds slots. One of the radios initiates transmission and maintains power control and time synchronization normally done by a base station. A network control station can voluntarily, or by command, transfer control of the network to any of the other radios on the network. Colliding transmissions from more than one radio require the radios to retry transmitting until one of the radios transmits in an earlier time slot. Conversational mode capability is provided by equipping the radio receivers with despreaders in parallel for permitting a receiving radio to separately despread the simultaneously transmitted signals, all other radios on the network and responding to each radio transmission individually. Simultaneous voice and data communications can be accomplished by equipping the receivers with despreaders for discriminating voice and data information signals spread by different PN codes. The ad-hoc, peer-to-peer radio system of the present invention is based on a transport-mechanism using a time division duplex (TDD) technique in a code division multiple access (CDMA) system. Time Division Duplex (TDD) is a way of maximizing the bits/hz/km2. Such a system not only may be used for providing commercial voice, but is also quite suited to both transmission and reception of data and video services. Time Division Duplex (TDD) systems are typically used for packet data systems, since they make much more efficient use of the available bandwidth, in order to deliver a much higher effective data rate to the end user. TDD is typically used in fixed wired solutions or point-to-point wireless systems because it has its own spectrum limitations. TDD systems, however, have not hitherto been deployed for voice systems.
Past research has shown that conventional Carrier Sense Multiple Access (CSMA) algorithms experience diminishing returns when networks approach their ultimate capacity. The vast majority of current research centers on channel access algorithms that provide transmission capacity over a single shared medium. An example of this is the IEEE 802.11 wireless standard which employs a Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) algorithm. All users within a Basic Service Set (BSS) share a common channel resource.
Reference is also had to copending, commonly-owned U.S. patent application Ser. No. 09/815,164, filed on Mar. 22, 2001, entitled “Prioritized-Routing for an Ad-Hoc, Peer-to-Peer, Mobile Radio Access System”, in which there is disclosed an example of routing table messaging which may be used in the present invention.
Reference is also had to commonly-owned pending provisional patent application Ser. No. 60/297,769, filed on Jun. 14, 2001, entitled “embedded Routing Algorithms under the Internet Protocol Routing Layer in a Software Architecture Protocol Stack”. The protocol stack of the system of this application defines the various algorithms used in establishing the connection of a radio terminal of the ad-hoc, peer-to-peer radio system disclosed in the present invention within its neighborhood of other terminals, with a gateway, and for setting necessary parameters for setting up and receiving calls, and updating necessary routing, power-level, quality-of-service parameters, as well as other essential processes used in the ad-hoc system of the present invention.